/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.druid.query.aggregation.datasketches.kll;

import org.apache.datasketches.kll.KllSketch;
import org.apache.druid.query.aggregation.Aggregator;
import org.apache.druid.query.aggregation.BufferAggregator;
import org.apache.druid.segment.ColumnSelectorFactory;
import org.apache.druid.segment.ColumnValueSelector;
import org.apache.druid.segment.NilColumnValueSelector;

import javax.annotation.Nullable;

abstract class KllSketchMergeAggregatorFactory<SketchType extends KllSketch, ValueType>
    extends KllSketchAggregatorFactory<SketchType, ValueType>
{
  public KllSketchMergeAggregatorFactory(
      final String name,
      final String fieldName,
      @Nullable final Integer k,
      @Nullable final Long maxStreamLength,
      final byte cacheTypeId
  )
  {
    super(
        name,
        fieldName,
        k,
        maxStreamLength,
        cacheTypeId
    );
  }

  @Override
  public Aggregator factorize(final ColumnSelectorFactory metricFactory)
  {
    final ColumnValueSelector<SketchType> selector = metricFactory.makeColumnValueSelector(getFieldName());
    if (selector instanceof NilColumnValueSelector) {
      return new KllSketchNoOpAggregator<SketchType>(getEmptySketch());
    }
    return getMergeAggregator(selector);
  }

  @Override
  public BufferAggregator factorizeBuffered(final ColumnSelectorFactory metricFactory)
  {
    final ColumnValueSelector<SketchType> selector = metricFactory.makeColumnValueSelector(getFieldName());
    if (selector instanceof NilColumnValueSelector) {
      return new KllSketchNoOpBufferAggregator<SketchType>(getEmptySketch());
    }
    return getMergeBufferAggregator(selector);
  }
}
